The present invention generally relates to brake systems and more particularly relates to a brake system for motor vehicles with an integrated electromechanic parking brake function.
German patent specification DE 39 09 907 C2 discloses a brake system for motor vehicles with a parking brake. The parking brake comprises a parking or brake lever, which is operable by the driver and permits acting upon a brake cable to release and apply the wheel brakes irrespective of a drive unit. Further, the parking brake includes a control device which is designed as a control electronics and, on the inlet side, is connected to at least one rotational speed sensor for sensing the wheel speed, to at least one direction-of-rotation sensor for detecting the direction of rotation of a wheel, and to a switch lever position sensor for detecting the switch lever position characteristic of a selected gear of a shift transmission. In dependence on the sensor data evaluated by the control electronics, the prior art parking brake may also be operated, i.e., tensioned or released, automatically, without any action by the driver, as soon as the vehicle is in a parking or driving situation which necessitates tensioning or releasing of the parking brake.
It is disadvantageous in this prior art arrangement of a parking brake that only an inappropriate driving-situation-responsive execution of the request of a driver is provided because a possible automatic brake intervention is intended only during standstill of the vehicle or at very low speeds. In addition, the parking brake reacts to manual actuation by the driver only in a mode of operation where the parameters of the driving condition do not have any basic influence on the actual execution of the brake operation.
It is likewise known from EP 0 825 081 A1 to realize an automatic starting-traction control function by means of a parking brake system operated by independent force. In general, it is necessary to evaluate and further process several input data characterizing the driving condition of the vehicle, within a control unit in the sense of release criteria for the automatic starting-traction control function. In parallel, corresponding input signals are sent to the control unit which characterize the driver""s request with respect to the parking brake actuation. This necessitates an extremely complex total structure of the control unit and the processing of large data volumes.
Based on the above, an object of the present invention is to provide a brake system with an integrated electromechanic parking brake function and an automatic brake-specific driving assistance function, wherein the different brake requirements are coordinated and realized in dependence on the driving situation.
The brake system of the present invention comprises an electromechanic parking brake device (EPB=electric parking brake) which has an operating element for detecting the driver""s request for brake actuation. Further, the brake system includes an electronic driver assistance device for the automatic execution of at least one brake-specific driver assistance function (e.g. starting-traction control, hill holder, traffic lights stop, parking assistance, etc.) which is able to automatically act upon the brake system in the sense of an active parking brake APB.
The brake functions are executed accordingly within the brake system by means of an electronically operable actuator device for the actuation of at least one wheel brake. An electronic control device for the conversion of input signals into corresponding output signals for the actuation of the actuator device finally ensures the controlled application or release of the wheel brakes. The input signals include the operating condition of the motor vehicle or the condition of operating devices of the motor vehicle. Both the current vehicle dynamics data and the operating data defined by the condition of the operating device (accelerator pedal, brake pedal, parking brake lever or pedal, clutch pedal, gear selector lever or pedal, etc.) are sent to the control device and processed by it.
The actual control device has a modular design, and independent software modules are produced which can be developed separately of one another as the purpose may be. A first software module (EPB module) serves for the conversion of input signals into corresponding signals for the execution of a parking brake function induced by the driver. Another module, i.e., a second module (APB module) generates from the input signals signals for the execution of the automatic driver assistance function which is implemented within the driver assistance device with its specific marginal conditions inside the brake system. The modular design of the software packages within the control device permits an improved and, in particular, quicker data flow which enhances the performance of the control device in total. Further, the modular software design permits a configuration of the individual modules related to their purpose and application and integration of them into the control unit in a simple fashion. Moreover, additional driver assistance functions can easily be inserted into the total system by a supplementary software component. It is this way possible that brake systems which are already provided with an electric parking brake device are supplemented with additional driver assistance functions to achieve an active parking brake APB.
Designing the control device with a first module for basically processing input data which gather the driver""s request for brake actuation, and a second module which processes data for the execution of automatic and brake-specific driver assistance functions provides a coordination module according to a favorable embodiment in which the signals supplied by the two modules are processed to resulting signals. The said signals are appropriate for the actuation of an actuator device which is connected to the wheel brakes. The objective of the coordination module is to generate output signals from the signals arriving from the two software modules connected upstream.
The present invention also includes a method for controlling a method brake system. In general, output signals which result from the incoming input signals are produced within the control device, the said output signals representing to the subsequent actuator device instantaneous nominal values for the actuating force end value Fres and the value of the force variation {dot over (F)}res (time derivative of the instantaneous force actual value) to be used therefor. The actuator device can be controlled by way of these output signals Fres, {dot over (F)}res in an application oriented manner and in response to the driving situation. As input signals for the control device, corresponding data relating to the driving condition of the motor vehicle (engine torque, vehicle speed, condition of the ignition system, etc.) are gathered, on the one hand, and condition data of the operating devices actuatable by the driver are acquired, on the other hand, by way of which data the driver can take influence on the operating condition of the motor vehicle (accelerator pedal, brake pedal, clutch pedal, parking brake switch/lever/pedal, ignition system, engaged gear, etc.). The input signals gathered by the control device are sent to the two software modules (EPB/APB modules) and processed by them. The first EPB module includes an operating concept for the driving-situation responsive actuation of the parking brake and, apart from data about the operating condition of the vehicle, considers in first place the driver""s request for brake actuation. From this, signals FEPB and {dot over (F)}EPB are generated in the EPB module which principally correspond to the instructions for the actuator device.
In parallel, the input data received from the control device are sent to the APB module which, in the sense of an active parking brake, can put into practice additional automatic driver assistance systems such as starting-traction control, hill holder, maneuvering aid/parking assistance system, etc. Requirement signals FAPB and {dot over (F)}APB which analogously correspond to the first module are generated by the APB module. The data supplied by the EPB and APB module are sent to a coordination module which compares and evaluates the corresponding data. Resulting output signals Fres and {dot over (F)}res which are used for the actuation of the subsequent actuator device are generated by the coordination module in dependence on the requirement values FEPB, {dot over (F)}EPB, FAPB, {dot over (F)}APB. The coordination unit as such must ensure that the driver""s request for brake actuation has priority in being considered, on the one hand, and that the specification is satisfied, on the other hand, to reach the resulting force end value with a dynamics that depends on the driving condition.